Mass spectrometer apparatus



Jan. 8, 1952 A. o. c. NIER 2,582,150

MAss SPECTROMETER APPARATUS Filed April 2, 1951 5 Sheets-Sheet 1INVENTOR. 144 FEED 0. C. NIEE ATTQENEK:

Jan. 8, A, O, c, ER

MASS SPECTROMETER APPARATUS 5 Sheets-Sheet 2 Filed April 2 1951 AVVENTOE/IL FEED 0. C N152 ATTORNEYS Patented Jan. 8, 1952 MASS SPECTROMETERAPPARATUS Alfred 0. o. Nier, Minneapolis, Minn., assignor to Regents ofthe University of Minnesota, Minneapolis, Minn., a corporationofMinnesota Application April 2, 1951, Serial No. 218,712

13 Claims.

In general it may be stated that a mass spectrometer consists of ahighly evacuated vessel having an electron source that is utilized forcharging atoms or molecules so that they exist within the vessel asions. The evacuated vessel is so constructed that it presents a path oftravel for the ions, which are accelerated by a suitable potentialgradient so that they travel along said path and collectively constitutean electric current. The path of travel includes a certain section whichis through a strong magnetic field which serves to deflect the movingions to a degree depending upon their masses and the strength of themagnetic field whereupon after further travel they are collected and theion current which they represent is measured or otherwise utilized.

In instruments of this character, the sample which is in the gas phaseis introduced into the mass spectrometer tube in the region of thefilament thereof, whereupon the molecules or atoms of the sample (whichmay be a mixture-of many materials) become ionized. The components ofthe sample are separated or analyzed by the functioning of the massspectrometer and an indication (or indications) provided by which theexistence of the proportion of various components of the sample can bedetermined.

The proper functioning of the mass spectrometer in analyzing samplesrequires, first, that the sample be introduced into the massspectrometer in very small amounts, preferably continuously; and second,that the act or apparatus used for introducing the sample in and ofitself should not fractionate the sample, for the composition of thesample must have a known relation to the same composition when it isinside the mass spectrometer tube. In addition where sampling is done ona continuous basis the sampling system should not introduce any unduedelay between the time the sample is taken and the time it is analyzed.

It is therefore an object of the present invention to provide animproved mass spectrometer gas analyzing device and particularly toprovide amass spectrometer wherein the gassample is introduced in minuteamounts and without fracticnating the sample in so doing, and withoutundue delay.

It is also an object of this invention to provide an improved,non-fractionating gas sampling device for use in conjunction with gasanalyzing mass spectrometers of simple, economical construction which iseasily adjustable and convenient to service.

It is also an object of this invention to provide a gas sample supplyfor a mass spectrometer which is adapted for accurate control of minutequantities of gas which are admitted to the system.

Other and further objects of this invention are those inherent in theapparatus herein illustrated, described and claimed.

The invention is illustrated with reference to the drawings in which:

Figure l is a side elevational view of mass spectrometer embodying theinstant invention;

Figure 2 is a somewhat enlarged, partially schematic side elevationalview of portions of the apparatus shown separated from the frame of the-machine in order to show the details more of the instant inventionshown in Figure 1, Fig- I ure 3 being illustrated partially in section,the

section being along the line in the direction of arrows 33 of Figure 4;

Figure 4 is a side sectional view of the com-- ponent shown in Figure 3,taken along the line .and in the direction of the arrows 4-4 of ure 3;

Figure 5 is an end sectional view of-the component shown in Figure 3,taken along the line and in the direction of arrows 5-5 of Figure 3;

Figure 6 is an enlarged fragmentary sectional view taken along the lineand in the direction of arrows 6-6 of Figure 3.

Referring to the drawings, Figure 1 particularly, the apparatuscomprises a main frame which may conveniently be composed of angleirons. The frame has a floor angle l0, posts II and I2 and intermediateframe member l3 and top frame member 14. Upon the intermediate framemember there is mounted the magnet assembly generally designated l5which may be either an electromagnet as illustrated or a permanentillustrated has a core I6 and a winding I8. The core has an air gapwhich is defined by pole pieces having the configuration shown by thedotted line I9. The core, which is U-shaped in plan view, has aninterior opening 29 between the legs of the U and between the coil andthe rear core connection 2| through which some of the supporting bracketstructure passes, as hereinafter defined. The entire core structure isassembled by means of the heavy bolts 22 and is fastened to the frame byfastening devices so as to be fixed on the frame.

Upon the upper surface of the core there is provided a bracket 24 ofopen box formation having upwardly extending supports 25. The brackethas a cap portion 26 whichis provided with matching downwardly extendinglegs 28 which meet the upwardly extending supports 25 at the separatingline 2929. The portions 2525 and 28-28 are provided with a circularaperture 30, not shown, through which the tubular connection 3| of theevacuatable system is adapted to pass. The two portions 24 and 26 of thebracket are held in clamping relation by a pair of studs 32 only one ofwhich is shown which are tapped into the upper surface of the magnetcore 21. The studs are provided with nuts at 33 which when pulled downexert a clamping pressure upon the tubular connection 3|. By looseningthe nuts 33 the tubular connection may be moved back and forth in thedirection of the double arrow 34 and to a limited extent the bracket24-26 may be rotated so as to exert a slight rotary motion on theevacuatable assembly for adjustment as hereinafter described. Inaddition, by inserting or removing shims between the lower surface ofthe bracket 24 and the upper surface of the core 2I at the level 35, itis possible to raise and lower the evacuatable assembly slight amountsfor adjustment purposes.

The evacuatable assembly consists of a tubular cross connection 3| whichis provided at its right end, as--shown in the drawings, with adownwardly extending branch 31 which'terminates in the flange 38. Theunder side of the flange 3B is ground so as to provide a spherical seatat 39 which fits the spherical connection 40 of the glass mercurydiffusion pump apparatus shown generally opposite the bracket 4 I. Thediffusion pump includes a vertical outlet tube 42 which leadsdownwardlyinto the moisture freezing trap bulb 43 to which it is sealedat 44. From the trap 43 there is aside arm 45'extending to the mercuryvaporpump section at 46. The mercury vapor pump is provided from themercury boiler 47 which is heated by an electrical heating element 48,the vaporized mercury passing upwardly through the tube 49 and thence tothe pumping section 46 where the pumping action takes place and themercury is incidentally condensed to liquid form which returns from thebulb 59 and thence via pipe to themercury boiler 41. The gases andvapors withdrawn by the mercury pump are delivered at the outlet tube 52which is connected by a flexible rubber' hose or other flexible lead 53to the pipe 54, Figure 1, which leads through the control valve 55 andline 56, flexible connection 56 to the fore-pump 60 which can be of anysuitable variety and driven by motor 6| mounted upon the bed plate 62that is in turn mounted upon the main frame members I0. Valve 64provides for breaking the vacuum when desired and valve 55 for closingoff line 54.

'ple becomes The seal of the spherical connection between the glass ball40 and the metallic spherical seat 39 is made by coating the memberswith ordinary red sealing wax which is heated and the two parts pushedfirmly together, after which they are permitted to cool. A cooling coil65 is soldered to the metallic flange 3B for cooling the flange duringgassing out operations, hereinafter described, so as to prevent damageto the seal.

At its left end, as shown in the drawings, Figures l and 2, the tubularcross connection 3| is joined to the mass spectrometer tube whichincludes an upper straight tubular section 66 of circular cross sectionwhich is reduced slightly at 6! and joined to the segmental curvedtubular section 68- which is in turn connected to the straight tubularsection 69 terminated in the ion collector I9. The curved segmentalportion 68 is flattened in cross section so as efficiently to occupy thespace between the pole faces I9. At the upper end of the straightsection 66 there is a flange I2 which is arranged to be cooled by thesoldered-on cooling pipe I3. To the flange I0 there is connected amating flange I4 which is held'by suitable clamping bolts; Flange I4 islikewise arranged to be cooled by the solderedon cooling coil I5. Uponthe flange I4 there is mounted the'entire ion source assembly shownopposite the bracket I6 which is suitably mounted and connected to theincoming leads 11 that are in turn connected to the separable coupling91. To the flange 14 there is also connected the inlet pipe I26 whichextends, as illustrated in Figure 2, into the interior of the ion sourcedelivering into the chamber I9 containing the electron emitter filament80. The sample undergoing analysis is introduced via tube I26 and isthus delivered into the region of the electron emitting filament 86'where due to electron emission the samionized. The ionized sample iswithdrawn from the chamber I9 through the slit M by a system ofpotential gradient plates 82. The plates 82 serve not only to acceleratethe ionized sample, but also to focus it in a beam of ions which passesin the direction of the dotted line 83, thence downwardly along the tubeportion 66 until it entersinto the strong magnetic field defined by thepole pieces I9. The ionized particles of the sample behave as anelectric current and'are deflected by the magnetic field along thecurved path 84 in an amount depending upon the strength of the magneticfield, the velocity of the particles and their mass. The velocity ismaintained constant or as nearly constant as possible, and since thesame magnetic field is common to all of the ionized particles, theamount of deflection occasioned by their passage through the strongmagnetic field is, therefore, dependent upon the mass of the particles.Consequently, the stream of ionized particles after having passedthrough the magnetic field emerges as a spectrum 85, the lighter ionizedparticles being deflected most, as exemplifled by the dotted line 86,and heavier particles deflected least, as exemplified by the dotted line81. The particles are caught upon separate ion collecting plates 88 andB9 of the ion collector mechanism M! where they give up their charges tothe plates. The charges upon plates 88 and 89 constitute the efiectivesignal and these are communicated by leads 96 and 9I which pass outthrough the glass squash 92 and thence through the flexible (Sylphonbellows) housing 93 to separate pre-amplifiers in the commonpreamplifier chamber 94 which is cushion-mounted by means of themounting 95 that rests upon the bracket 96 attached to the frame membersl I.

Referring to Figures 3-6, the mechanism by which the gas sample isintroduced into the mass spectrometer mechanism which is illustrated inthose figures and is shown opposite brackets 99 in Figure 1 includes abase plate I20 which may be mounted in any convenient plane such ashorizontally or vertically by means of fastenings placed throughopenings I2I. Adjacent one end of the plate there is a block I22 whichis preferably removably attached by screws I23-I23. The

block I22 serves to support inlet tube I24 which.

is connected at its exterior end I25 to the sample source which is atrelatively high pressure, which is customarily in the range of to 200mm. of mercury pressure. Block I22 also serves to sup port the outlettube I26 which is connected at its exterior end I2I to the inlet tube ofthe mass spectrometer. Tube I26 is accordingly maintained at the lowpressure maintained in the mass spectrometer tube, which is customarilyheld in the range of 10- to 10' mm. of mercury pressure.

Both tube I24 which is connected to the gas sample supply and tube I26which is connected to the mass spectrometer as shown in Figures 1 and 2are fastened to the block by soldering or brazing, shown at I28 and I29.The inner end I30 of tube I32 which is connected to tube I24 by a metaladapter I 34 between the two tubes and the adapter being made gas-tightas by soldering.

The capillary tube I32 then continues through a long course of travel,length L, including turns I35 and goes through the constrictiongenerally designated I36 and then continues through a short travel Sfrom the constriction I36 to the end I31 of tube I36 to which it isattached in gastight relation by means of an adapter I38 to which bothtubes are soldered. The entire tube I32 and constriction I36 is coveredby housing cup I40 which is held in place by a single cap screw I42,which is of the recessed head (Allen) type and is threaded into baseI20. The cup is notched out at I48 and I49 to permit entry of tubes I24and [26.

The constriction I36 of capillary tube I32 is constructed by passing thetube I32 under a simple clamp bar I43 that is arranged to be drawn downby the recessed head cap screws I44 and I45 that pass through holes inbar I43 and are threaded into base I20. The lower edgesof bar I43 arerounded off at I46 and I48 so as not to present a sharp corner to thetube I42 which is engaged and flattened as the bag,' I43 is drawn down.The pressure of clamp bar I43 on capillary tube I32 flattens the tubethroughout the area I4? and restricts its cross-sectional area to anydesired degree thus throttling the gas sample. By loosening screws I44and I45 the pressure on clamp bar I43 may be relieved and, due to theresiliency of the tube, it tends to spring open and increase thecross-sectional area at the restriction. This permits ready adjustmentof the constriction of the capillary tube.

In a typical installation in accordance with this invention the totallength (L plus S) of capillary tube was 20 inches, the tube being ofseamless, hard drawn copper tubing having an inside diameter of .003inch. The constriction was in this installation about one inch from tubeI26; length S was, therefore, approximately one inch.

The purpose of the long length L of capillary tubing is to prevent backdiffusion of gas, and hence fractionation at the constriction where acombination of viscous and molecular flow takes place. In accordancewith this invention the capillary diameter and length L are chosen sothat the mass flow velocity of the sample in the capillary tube towardthe constriction I4? will be greater than the back difiusion velocity ofany component of the gas mixture through the constriction I41. Hence,the gas sample entering tube I26 leading to the spectrometer will berepresentative of that in the supply manifold tube I24 from containerI00. By thus choosing the capillary tube length L and its insidediameter so as to insure having a mass flow velocity of the gas sample(through the capillary tube portion L) which is greater than the backdiffusion velocity of any component through the constriction I4'I, it ispossible to insure against fractionation of the sample at theconstriction even when the gas sample is a complex mixture consisting ofconstituents of widely differing viscosity and widely varying molecularweights.

In general it may be stated that in accordance with my discovery, thecapillary tube should have an inside diameter of not less than .002 inchand preferably not more than .012 inch. The length L for such tubeshould be not substantially less than 15 inches and I prefer to use acapillary tube not less than 20 inches for the length L, thus a length Lin the range of 20 to inches gives good results, the length S being asshort as practically possible. There is no fixed maximum for length Lbut L should not be appreciably less than 15 inches. Even greaterlengths than 100 inches may be used where the time delay factor is not adisadvantage. The length S should be kept short enough so that there islittle pressure drop through this portion of the capillary tube so asnot to cause the gases flowing therethrough to have a viscous flow. Thelength S should preferably be not more than two to three inches, and inmost installations can be kept to a length of about 1 inch without unduemechanical difficulty.

Thus, an excellent gas sampling orifice was composed of capillary tubehaving an inside diameter of .007 inch, a length S of 1 inch and alength L of approximately 40 inches and constricted as shown in Figures3 and 6. Another excellent gas sampling orifice utilized a capillarytube having an inside diameter of .010 inch, 2. length S ofapproximately 1 inch and a length L of approximately 20 inches andconstricted as shown in Figures 3 and 6. For most installations I preferthat the capillary tube have an inside diameter not smaller than .004inch and a practical lower limit of the tube is .002 inch.

Best results are obtained if the pressure in the sample tube I24 is notless than 10 cm. of mercury. The pressure in the sample tube can beincreased without difficulty. The constriction caused by the squeezeimposed on the capillary tube by the bar I36 limits the flow through thecapillary tube at the constriction to approximately 1 cubic centimeterof gas in 24 hours calculated at normal pressure and temperature. Thesqueeze can be adjusted more or less so as to maintain the massspectrometer in the correct pressure operating range, as hereinbeforestated. Most mass spectrometers have an operating pressure of about 10-mm. of mercury and an operating range of from 10* to 10- mm. of mercury.The range that is customarily held is from 10- to 10- mm. of mercury, aspreviously stated herein. If the gas in the mass spectrometer isinsufiicient (i. e. the pressure decreases) the mass spectrometerbecomes less sensitive.

7 If the pressure in the mass spectrometer. increases, the, ions thatare generated tend to scatter and the operation of the massspectrometerbecomes erratic. By adjusting the squeeze on the capillary tube I32, asprovided by the squeezing bar I36, it is possible to regulate theconstriction sothat just the proper amount of gas rushes through theconstriction so as to maintain the pressure within the mass spectrometerin the appropriate range for best action.

The diffusion cofiicients and viscosity coefficients of various gases donot vary a great deal so that one settingcr" the constriction bar I36will be satisfactory for. most gases ordinarily analyzed.

If the length L of the capillary tube is in creased, the operator maypermissibly use lower pressure in the gas supply tube I2 5, butincreased. length L. of the capillary tube offers. a disadvantage inthat a greater time is required to pull a given unit quantity of gasthrough the increased length of capillary tube. Thus, where the sampling.orifice forms a part of a mass spectrometer system for continuousanalysis of gas, there would be a time lag in the indication of theinstrument, and the instrument would lways read what the gas compositionhad been a given time period previously. This is because the amount ofgas fillingthe capillary tube has to be drawn therethrough. According,from this standpoint it is desirable to select the length L as short aspossible, so as to decrease this time lag. Where the time lag factor isno disadvantage, an increase in length ofiers no objection.

t is desirable to make the inside diameter of the capillary tube smallso that the gas through it will flow more rapidly (with a massfiowvelocity), but the inside diameter should not be so small as toproduce a molecular flow. Thus, if exceedingly small capillary tubes, astubes below .002 inch I. D. is used, such tubes will produce a molecularflow with consequent fractionation at most sample pressures.

The back diffusion of gases through the constriction of the tube underthe squeeze bar I36 can be overcome by keeping. the flow through theconstriction fast enough and by utilizing a tube length L notsubstantially less than inches long and preferably or more inches long.The longer tube length L that is provided, allows the gases on thesample side of the constriction to diffuse back far enough so that theconcentration of the back-diffused gases per unit of volume remainsnegligibly small.

The lighter gases go through the constriction faster than the heaviergases, and the heavier gases accordingly build up on the sample side orthe constriction. Difficulty due to. increase of such concentration iseliminated by utilizing a tube having an inside diameter in the range offrom about .002 inch to .012 inch and a length L not substantially lessthan 15, inches and preferably 20 or more inches, the length S meanwhilekept relatively much shorter, viz. not substantially more than 3, inchesand preferably about 1 inch or less.

In prior instruments used for laboratory analysis of complex gasmixtures, the problem was solved by having the sample at very lowpressures so as to insure that true molecular flow conditions existed.By using the apparatus of the present inventionfone is not limited tothe use of gas samples at low pressures. The apparatus is thus adaptedfor continuous analysis of gases fromany source of gas connected to tubeI24 which may be under positive or negative gauge pressure, so long asthe source pressure is positive in respect to that in the. tube I26.

Various adjuncts of the mass spectrometer tube include the framework telwhich is mounted upon the tubular cross connection 3!, as shown inFigure 1. Element itl has been eliminated in Figure 2 for purposes ofclarity. The frame work IGI which is suitably adjustable upon tube 3iserves in turn adjustably to support the frame I02 which is of horseshoe configuration in bracing the tube fiii, the horse shoe frame I92carries permanent focusing magnets. A further focusing magnet assemblyis illustrated at I83, this being carried upon the frame hid whichlikewise is adjustably mounted upon the tube 69. At the right end of thetubular connection 3| there is a, branch I05 which extends to thePhillips gauge mechanism I96 which, per se, forms no part of the presentinvention. The Phillips gauge mechanism is a very sensitive pressuremeasuring device operating on the electron bombardment principle.

Extending downwardly from the tubular cross connection 3I there is aninterior support brace rod Iii! which is clamped to the tubularconnection by means or the clamping bracket I08. The brace rod iii?extends down between the spaced legs of the large magnet I5 and isconnected at its lower end to the mercury diffusion pump mechanism il soas to support it.

Upon the rear of the main frame there is a vertical bracket rod lit uponwhich there is adjustably mounted the side arm bracket HI supporting theplate H2. The plate II2 serves to carry an open top Dewar flask i itinto which the bulb 33 of the freezingtrap in the mercury diffusion pumpis adapted to be immersed. The

\ brace Iii may be loosened by unscrewing the wing nut lid so as topermit lowering of the Dewar flask M3 for replenishing the liquid airsupply therein and by the same adjustment the Dewar flask may bepositioned so that the bulb as is submerged into the flask and yet notin contact with it.

For the most part the mass spectrometer tube is composed of an alloysuch as Inconel (trademark) or other suitable high temperature alloy.Thus, the tubular cross connections 3| and the ion path tube consistingof branches 65, Bl, 68 and 89, the flanges i2 and I4 and the metallicportions of the ion collector mechanism l0, as well as the branch 37leading to the mercury diffusion pump ,and the branch Hi5 leading to thePhillips gau ge are all made of such alloy. In placing the apparatus inoperation it is necessary to degas it by heating these metallic parts,and yet certain areas of the apparatus must not be heated beyondprescribed temperatures, otherwise gaskets, etc. will be deteriorated.In order to provide local cooling, cooling water tubes are soldered onat the prescribed places. Thus, a cooling Water tube 65 is soldered ontothe flange 33, thus chilling it Whiie the adjacent portions are heated,thus preventing the softening of the red sealing Wax by which the joint3940 is sealed. Cooling water tubes are also soldered onto the flangesi2 and "all as indicated at I3 and its. All the cooling water tubes areconnected in series or parallel, as desired. Other cooling water tubesH1 and H8 extend down to the mercury diffusion pump connections II9 andI20, respectively.

It will be observed that in the described structure the entire massspectrometer tube, including diffusion pump which hangs as a pendulousmass at the right end, being partly supported through the connection 31and partly through the brace rod I01. At the left end of the tube 3 l,as shown in the drawings, there is the ion path defined by thetubes56-69 having at the upper end the ion source assembly 16 and itsappropriate con' nections and adjuncts and at the lower end the ioncollector 10. In addition, all the adjuncts, including the focusingmagnet assemblies I02, I03 and the Phillips gauge I 06 are mounted uponthe evacuatable assembly and are supported through it upon the bracket2426. Consequently, by loosening the bracket 2426 it is possible toshift the entire evacuatable assembly with reference to the magnet l andthus obtain precision adjustment of the ion beam 83 with reference tothe pole pieces l9. It will be noted that the pole pieces 19 define asegment of sixty degrees and that the ion source 15 and ion collector l0are aligned as indicated at IN. The focusing and adjustment arecritical, and for best results may in the present apparatus be made by asingle simple adjustment, whereas heretofore the adjustment has had tobe made by movement of the heavy magnet [5, a cumbersome adjustment atbest.

In the illustrated form of the invention the preamplifier 94 is mountedon the frame H and connected to the mass spectrometer tube at theflexible connection 93 which permits movement of the tube relative tothe preamplifier case 94. If desired, however, the preamplifier may beconstructed of light weight materials and hung on the lower end of thetube 69 adjacent the ion collector plates. Likewise, if desired, thefore-pump 60 and its drive motor may be hung from the brace rod I01which may also support the plate H2 for supporting the Dewar flask H3 ofthe freezing trap.

If the mass spectrometer tube is made movable and the high vacuum pumpstationary so as to allow the mass spectrometer tube to be moved withoutmoving the pump, this involves the provision of a flexible high vacuumconnection between the two elements. this kind can be made by employingSylphon bellows, they are never completely satisfactory. A Sylphonbellows has a great deal of surface area and hence is diflicult to gasout satisfactorily. Moreover, they are subject to vacuum leaks.

As many apparently widely different embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that I do not limit myself to the specific embodiments hereinexcept as defined by the appended claims.

What I claim is:

1. In a mass spectrometer having a gas sample inlet the improvementcomprising a non-fractionating gas sampling device comprising a gassample supply tube, a long capillary tube having a gas passagecompletely therethrough connected to the mass spectrometer gas samplesupply tube and to said spectrometer gas sample inlet, a constriction inthe capillary tube located relatively While connections of closer tospectrometer gas-sample inlet than to the gas sample supply tube, thesize of the capillarytube and the degree of constriction thereof beingsuch that the mass flow velocity of gases through the tube is greaterthan the back diffusion velocity of said gases at said constriction.

2. Ina mass spectrometer having a gas sample inlet, the improvementcomprising a gas sample supply tube, a long capillary tube having oneend connected to said supply tube and having the other end of saidcapillary connected to the gas sample inlet of said mass spectrometer,said capillary tube having a constriction adjacent the gas sample inletof said mass spectrometer, said capillary tube having an internaldiameter of not substantially less than .002" and a length from saidconstriction to said supply tube not substantially less than 15 inches.

3. The apparatus ofclaim 2 further characterized in that theconstriction of the capillary tube is formed by flattening the capillarytube.

4. The apparatus of claim 2 further characterized in that said capillarytube is flattened by being clamped between two "plates and means issupplied for drawing the plates together to vary the degree of clampingpressure.

5. In a mass spectrometer having a gas sample inlet, the improvementcomprising a gas sample supply tube, a long capillary tube having oneend connected to said supply tube and having the other end of saidcapillary connected to the gas sample inlet of said mass spectrometer,said tube having an inside diameter in the range of approximately .002to .012 inch, said capillary tube having a constriction intermediate itsends, the length of said capillary tube from said constriction to saidsupply tube being not substantially less than 15 inches.

6. In a mass spectrometer system having a gas sample inlet, a gas sampleenclosure, a long capillary tube connecting said gas sample enclosure tothe gas sample inlet of said mass spectrometer, said capillary tubehaving an inside diameter in the range of approximately .002 to .012inch, a constriction in said capillary tube adjacent the gas sampleinlet of said mass spectrometer, the

length of said capillary tube from said constriction to said gas sampleenclosure being in the range of about 15 inches to about inches.

'7. In a mass spectrometer having a gas sample inlet, a gas sampleenclosure, a capillary tubular connecting said gas sample enclosure andsaid gas sample supply inlet of said mass spectrometer tube, saidcapillary tube having a constriction adjacent said gas sample supplyinlet of the mass spectrometer, the length. of said capillary tube fromsaid constriction to said gas sample enclosure being approximately 40inches and the inside diameter of said capillary tube beingapproximately .007 inch.

8. In a mass spectrometer having a gas sample inlet, a gas sampleenclosure, a capillary tubular connecting said gas sample enclosure andsaid gas sample supply inlet of said mass spectrometer tube, saidcapillary tube having a constriction adjacent said gas sample supplyinlet of the mass spectrometer, the length of said capillary tube fromsaid constriction to said gas sample enclosure being approximately 20inches and the inside diameter of said capillary tube beingapproximately .003 inch.

9. In a mass spectrometer the improvement comprising a non-fractionatinggas sampling device comprising supply and outlet tubes each having gaspassage ways therethrough, a length of capillary tubing which likewisehas a gas pasl l sageway therethrough connected to said tube so as to'forma continuous gas passageway from the supply tube to the outlet tubefor drawing a gas sample from said supply tube to said outlet tube,

and means contacting the capillary tube adjacent its point of connectionto the outlet tube for applying clamping pressure on the capillary tubefor flattening and thereby constricting the capillary tube.

10. The apparatus of claim 9 further characterized in that said-meansincludes a platealong which the capillary tube extends, a clamping barextending transversely across the capillary and means for drawing theclamping bar toward the plate with the capillary tube between forexerting pressure on the capillary tube to flatten and constrict theopening therethrough.

l1. Theapparatus of claimilo further characterized in that the platealso serves as a support for the supply and outlet tubeszand that thecap illary tube connectionbetween them is coiled by it and the clampingbar arercovered by a housing fastened onto the plate.

12. A'nonrfractionating :gas sampling device comprising supply andoutlet-tube each having a gas passageway therethrough, a length ofcapillary tubing which likewise has a gas passageway completelytherethrough connected to said tubes so as to form a continuous gaspassageway from the supply tube to the outlet tube for drawing a gassample from said supply tube to said outlet tube and means contactingthe capillarytube adjacent its point of connection to the outlet tubefor applying clamping pressure onto the capillary tube for flatteningand thereby constricting the capillary tube, said means including aplate along which the capillary tube extends and a clamping barextending transversely across the capillary tube and means for drawingthe clamping bar toward the plate with the capillary tube therebetween.

13. In a mass spectrometer analyzer the improvement which consists of anon-fractionating gas sampling device comprising supply and outlet tubeeach having gas passageways therethrough, said outlet tube beingconnected to said analyzer adjacent the filament region thereof, alength of capillary tubing having a gas passageway completelytherethrough connected to said tube so as to form a continuous gaspassageway from the supply tube .to the outlet tube for drawing a gassample from said supply tube to said outlet tube, and means contactingthe capillary tube adjacent its point of connection to the outlet tubefor supplying clamping pressure on the capillary tube for flattening andthereby constricting the capillary tube.

ALFRED O. C. NIER.

No references cited.

